This invention relates to a method for the selection of an available memory size of a circuit including at least a processor (for example a CPU, a microprocessor or a processing unit) and a memory.
This invention will be described here in the context of the manufacturing of a particular product, the smart card, but it may be applied to other products incorporating an electronic circuit, such as an integrated circuit, including a processor and a total memory. In this same example, a non volatile memory (NVM) may be mentioned, but the invention applies to all types of memory (NVM, RAM etc.)
FIG. 1 illustrates three suppliers of integrated circuits according to the earlier technique, X1, X2 and X3, supplying products to a smart card manufacturer. Each supplier has several products. In practice, however, the different products have the same processor and are only differentiated by different available memories in each product. That is the case, for example, in this FIG. 1, with supplier X1, and product numbers 300K, 320K, 340K and 360K. These products 300K, 320K, 340K and 360K each have the same processor but different available memory sizes, namely 300 Kbytes, 320 Kbytes, 340 Kbytes and 360 Kbytes respectively.
Further, in reality, the products have the same total memory size of 360 Kbytes, but in an ultimate stage of manufacturing/testing the circuit, the circuit manufacturer has elected to make only part of the memory available for addressing a specific need of its customers. In such a case, the circuit manufacturer “blocks” and makes inaccessible (and does not for instance test) that portion of the memory that is not made available and defined in this particular case by a memory size that is equal to the difference between (a)—360 Kbytes and (b)—the size of the memory made available.
The problem with this solution according to the earlier technique is as follows:                the selection by the circuit manufacturer of an available memory size for each circuit makes it necessary for the circuit manufacturer to implement elaborate personalisation stages (different tests, different production lines) while manufacturing the circuit, making the process more complex.        